anyway supposing I buy a rifle...good to 1/2 moa at 100 yds..specifically its a tikka t3..how do I got about getting a decent scope that isn't gonna cost more than the rifle. they can be had for about 5-800$.

I don't want what ya would recommend.

I wanna know how to select the scope I need based on the rifle I have.

im the other gary...

"The right and the decision to carry a weapon for your own defense is a horrible blessing".

Two things are infinite: the universe and human stupidity; and I'm not sure about the the universe."
einstein

Along with distance and caliber being used, lens clarity, light gathering, mechanical operation, weight, reticle or circle dots, and perhaps illumination are basics for choosing scopes.

I like 1-4x scopes with circle dots, plain and/or illuminated for out to 200 yards.
1-8x, 2-7x, or 3-9x for out to 400 yards.
If I was ever going to take a shot at more than 400 yards, a 3x-12 or 4x-12/16

Gary, I have a variety of scopes you can get an idea of what you might want.

Google pain in the ass and your picture should be there-sayeth my wife

IMHO the most important is the durability. You want a scope that you can sight in and not have to worry if it's the scope or the shooter when shots are not going where they should. You have to have confidence that your scope is always going to hold zero. This brings up the issue of mount and rings. Highest quality scope is not going to do any good if it's mounted to the rifle using cheap mount and rings. Like the scope, you want to have full confidence that your mount is never going to get loose or move. Put a great scope on the rifle with poor quality mount/rings and you'll most likely end up with sighting problems. Second most important characteristics is clarity and I find this to be more important as our vision gets worse with age. Unfortunately clarity requires high quality glass and optical quality glass is expensive. I find that I can compensate for lower magnification with sharper image. I remember reading once that the maximum practical range of a scope can be calculated by multiplying the top magnification by 50 for big game and by 25 for varmint and that will be the practical maximum distance in yards. So if you have 3-9X power then your maximum practical range for big game hunting would be (9x50) about 450 yards or for varmint hunting (9x25) about 225 yards. This is a just a guide but I think it's pretty close to reality for most of us. Finally, objective size (along with quality of glass) will partly determine the brightness of the scope at the upper magnifications. I think 40mm objective is for general purpose shooting while 50-56mm are for low light situations...but larger objective usually mean more weight and larger size scope.

The answer(s) are... target and range. If you are gonna shoot mice at 200 yds you need a biggie.... if you are gonna shoot buffalo's at 50 yds a smallie will work... if you are gonna shoot both critters, then something like a 4x16 variable might be needed... my $.02 worth.. RDK